Formic acid is a promising hydrogen carrier owing to
its high hydrogen density and liquid phase. Therefore, the production
of hydrogen from formic acid via catalytic dehydrogenation reaction
has been extensively studied. Various methods such as alloying of
the active Pd metal with other metals and adding dopants (e.g., the
amine-functional group, nitrogen, or metal oxide) have been suggested
to enhance the catalytic activities for formic acid dehydrogenation.
In this study, we synthesized carbon-supported palladium nanoparticles
coexisting with ceria particles and investigated the role of cerium
in this reaction over Pd/C catalysts. We made an effort not to change
the particle size and the electronic state of Pd significantly while
varying Ceria/Pd molar ratios in the catalysts, ruling out their effects
on the reaction. Ceria was impregnated on carbon by incipient wetness
impregnation; subsequently, Pd was impregnated on Ceria/C by deposition–precipitation.
The catalytic tests demonstrated that ceria improved the reaction
rate by producing formate anions, the main reactant of this reaction,
as it was dissolved by formic acid during the reaction. More importantly,
the dissolved cerium ions accelerated the reaction by interacting
with the formate anion to change its electronic charge, thereby reducing
the activation barrier for C–H bond cleavage. The carbon-supported
palladium nanoparticles promoted by cerium could be used to develop
a highly efficient hydrogen extraction system from formic acid.